Editing Visual memory (section)

== Neuroanatomy ==
In humans, areas specialized for [[Cognitive neuroscience of visual object recognition|visual object recognition]] in the [[Two Streams hypothesis#Ventra stream|ventral stream]] have a more inferior location in the [[Temporal lobe|temporal cortex]], whereas areas specialized for the visual-spatial location of objects in the [[Two Streams hypothesis#Dorsal stream|dorsal stream]] have a more superior location in the [[parietal cortex]]. However, these two streams hypothesis, although useful, are a simplification of the visual system because the two streams maintain intercommunication along their entire rostral course.

=== Posterior parietal cortex ===
[[File:Posterior Parietal Lobe.jpg|thumb|[[Posterior parietal cortex]] (light green) is shown at the posterior area of the [[parietal lobe]]]]

The [[posterior parietal cortex]] is a portion of the [[parietal lobe]], which manipulates mental images, and integrates sensory and motor portions of the brain.

A majority of experiments highlights a role of human posterior parietal cortex in visual [[working memory]] and attention. We therefore have to establish a clear separation of visual memory and attention from processes related to the planning of goal-directed motor behaviors.

We can only hold in mind a minute fraction of the visual scene. These mental representations are stored in visual short-term memory.<ref name="M3">Todd, J, & Marois, R. (2004). Capacity limit of visual short term memory in human posterior parietal cortex. Retrieved from http://www.ioi.knaw.nl/viscog/temp/Todd%20(2004)%20Nature.pdf</ref> Activity in the posterior parietal cortex is tightly correlated with the limited amount of scene information that can be stored in visual short-term memory.<ref name="M3" /> These results suggest that the posterior parietal cortex is a key neural locus of our impoverished mental representation of the visual world.<ref name="M3" />

The [[posterior cortex]] might act as a capacity-limited store for the representation of the visual scene, the frontal/prefrontal cortex might be necessary for the [[Memory consolidation|consolidation]] and/or maintenance of this store, especially during extended retention intervals.

=== Visual cortex ===
[[File:Ventral-dorsal streams.svg|thumb|The [[Two Streams hypothesis#Dorsal stream|dorsal stream]] (green) and [[Two Streams hypothesis#Ventral stream|ventral stream]] (purple) are both actively involved in visual memory. Both pathways originate in the [[visual cortex]].]]

There is a [[visual cortex]] in each [[Cerebral hemisphere|hemisphere]] of the brain, much of which is located in the [[Occipital lobe]]. The left hemisphere visual cortex receives signals mainly from the right visual field and the right visual cortex mainly from the left visual field, although each cortex receives a considerable amount of information from the ipsilateral visual field as well. The visual cortex also receives information from subcortical regions, such as the [[Lateral geniculate nucleus|lateral geniculate body]], located in the thalamus. However, ample evidence indicates that object identity and location are preferentially processed in ventral (occipito-temporal) and dorsal (occipito-parietal) cortical visual streams, respectively.<ref name="M3" />
Comparison of [[Molecular imaging#Single photon emission computed tomography (SPECT)|rCBF]] during performance of the two tasks again revealed differences between the ventral and dorsal pathways.<ref name="M3" />

==== Dorsal stream pathway ====
{{Main|Dorsal stream}}

The dorsal stream pathway is mainly involved in the visual-spatial location of objects in the external world, and it is also known colloquially as the 'where' pathway. The dorsal stream pathway is also involved in the guidance of movements (e.g., reaching for an object in space), and is therefore implicated in the  analysis of the movement of objects in addition to their spatial locations.

The dorsal stream pathway begins with purely visual information in the occipital lobe, and then this information is transferred to the parietal lobe for spatial awareness functions. Specifically, the posterior parietal cortex is essential for "the perception and interpretation of spatial relationships, accurate body image, and the learning of tasks involving coordination of the body in space."<ref>{{cite book|last=Bear|first=Mark|title=Neuroscience: Exploring the Brain|url=https://archive.org/details/neuroscienceexpl00mark|url-access=registration|date=2007|publisher=Lippincott Williams & Wilkins|location=Hagerstown, MD|isbn=978-0-7817-6003-4}}</ref>

==== Ventral stream pathway ====
{{Main|Ventral stream}}

The ventral stream pathway is mainly involved in object recognition, and is known colloquially as the 'what' pathway. It has connections to the medial temporal lobe (which is involved in the storage of long-term memories), the [[limbic system]] (which regulates emotions), and the dorsal stream pathway (which is involved in the visual-spatial locations and motions of objects). Therefore, the ventral stream pathway not only deals with the recognition of objects in the external world, but also the emotional judgement and analysis of these objects.

The ventral stream pathway begins with purely visual information in the primary visual cortex (occipital lobe), and then this information is transferred to the temporal lobe.

=== Occipital lobes ===
Located at the back of the brain, the [[occipital lobe]]s receive and process visual information. The occipital lobes also process colors and shapes. Whereas the right occipital lobe interprets images from the left visual space, the left occipital lobe interprets images from the right visual space. Damage to the occipital lobes can permanently damage visual perception<ref name="Mar">[The human brain. (2009, July). Retrieved from http://www.allabouttbi.com/partsofthebrain]</ref>

==== Occipital lobe injury complications ====
Damage to the occipital lobe is characterized by loss of visual capability and the inability to identify colors both important processes in visual memory.

=== Short term visual memory ===
{{Main|Visual short-term memory}}

Visual short term memory is the capacity for holding a small amount of visual information in mind in an active, readily available state for a short period of time (usually no more than 30 seconds). Although visual short term memory is essential for the execution of a wide array of perceptual and cognitive functions, and is supported by an extensive network of brain regions, its storage capacity is severely limited.<ref name="M3" />

Visual short-term memory storage is mediated by distinctive posterior brain mechanisms, such that capacity is determined both by a fixed number of objects and by object complexity.<ref name="M3" />

=== Long term visual memory ===
Recall of the patterns from long term visual memory is associated with [[Molecular imaging#Single photon emission computed tomography (SPECT)|rCBF]] increases in different areas of the [[prefrontal cortex]] and the [[anterior cingulate cortex]].<ref name="M3" />
The retrieval of long term visual memories is associated with activation of both anterior and posterior temporal cortices. Posterior temporal cortical regions are more associated with retrieval of category-specific aspects of visual memory, whereas anterior regions of the temporal cortex are more associated with category-independent visual memory.<ref>{{cite journal |last1=Takeda |first1=Masaki |title=Brain mechanisms of visual long-term memory retrieval in primates |journal=Neuroscience Research |date=May 2019 |volume=142 |pages=7–15 |doi=10.1016/j.neures.2018.06.005 |pmid=29964078 |doi-access=free }}</ref>